Unable to upgrade Ubuntu to 16.04 version from 15.10

[Andreu Correa Casablanca]

System:
    Ubuntu 15.10 64 bits.
    Linux castarco-desktop 4.2.0-35-generic #40-Ubuntu SMP Tue Mar 15 22:15:45 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

As an extra note, I'm using the privative Nvidia drivers provided by Ubuntu (not the ones provided by the NVIDIA webpage).

The upgrade manager is telling me that it can't upgrade my system to Ubuntu 16.04, but it does not tell me what's the concrete problem, this is too vague (this is a Spanish message that appears after computing the needed changes):

    Eso se ha podido causar por:
    * Actualizar a una versión de Ubuntu aún no publicada
    * Estar ejecutando la versión actual, aún no publicada, de Ubuntu
    * Paquetes no oficiales de software no proporcionados por Ubuntu

    Si nada de esto aplica, informe de este error usando la orden
    «ubuntu-bug ubuntu-release-upgrader-core» en una terminal.

ProblemType: Bug
DistroRelease: Ubuntu 15.10
Package: ubuntu-release-upgrader-core 1:15.10.14.4
ProcVersionSignature: Ubuntu 4.2.0-35.40-generic 4.2.8-ckt5
Uname: Linux 4.2.0-35-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.19.1-0ubuntu5
Architecture: amd64
CrashDB: ubuntu
Date: Sat Apr 30 18:08:48 2016
InstallationDate: Installed on 2015-09-03 (240 days ago)
InstallationMedia: Ubuntu 15.04 "Vivid Vervet" - Release amd64 (20150422)
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=es_ES
 TERM=xterm-256color
 PATH=(custom, no user)
 LANG=es_ES.UTF-8
 SHELL=/bin/bash
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to wily on 2016-04-30 (0 days ago)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Marian Krause (mkdugi)]

I've removed xserver-xorg-video-intel and xserver-xorg-video-nouveau and few others i don't need (I have AMD APU) and this bug "dissapeard" - system is upgrading now.

In apt.log we can find, that this packages creating dependiency problems apt cannot resolve.

[Marian Krause (mkdugi)]

It is enough to remove xserver-xorg-video-nouveau before do-release-upgrade.

[Brian Murray (brian-murray)]

This was because you had xorg packages installed from a PPA.

[Brian Murray (brian-murray)]

Reviewing the files from your upgrade attempt you seem to have enabled a PPA that provides Xorg packages. This will prevent the upgrade as that PPA contains different versions of packages essential to Ubuntu. The page, https://launchpad.net/~xorg-edgers/+archive/ppa, contains details on to how to revert to the official Xorg packages for the xorg-edgers PPA. Instructions for reverting to official Xorg packages should be similar for the PPA that you have enabled.